Movements of electrical measuring instruments and the like



E2 LIKE Sept. 29, 1953 G. N. HARDING ETAL MOVEMENTS OF ELECTRICAL MEASURING INSTRUMENTS AND TH Filed Oct. 26, 1949 Fig.2

GEORGE NELSON HARDYNG OTTO FRANZ WILHELM THAL Fig. 3

Inventors %M B N M I Attorneys Patented Sept. 29, 1953 memes ove-Mews or ELECTRICAL MEASURING INSTRUMENTS-1ND THE LIKE Gccrse N- H nd n A der-sno England, a d. Otto ranz W lhelm h B e eleld. German s gn s t Minister f S p l in His Maiestys Governmen t he Un ted King om f. G eat Britain and Northern Ireland, London, England ppli obcr26, 49, Sensible. 136.863. in Great Britain Septcmbes3, 194.8

4 Claims. o1. 324-151 s i vention e ates. to el ctrical. in t u and like movements in which a control torque is fforded by a permanent magnet instead of by a hair spring as in conventional moving-coil type indicators. It is customary in such ap Daratus for provision for limiting the total angular deflection of the usual spindle and armature. or rotor assembly to be made quite. independently 0f the control torque means.

According to the present invention, in an electrical instrument or like movement employing a permanent magnet to provide control torque, this magnet and a neighboring part of the moving assembly are shaped and positioned to co-act with one another at different angular positions of the moving assembly to limit the permitted deflection of the latter, whereby adjustment of the said permanent magnet about the axis of movement not only shifts the zero position of the moving assembly but at the same time shifts in the same sense about said axis both limits of the permitted angular deflection of the moving assembly.

The control magnet may extend at one end into the path of two spaced abutments on the moving assembly to co-act with one of said abutments to limit the angular movement in the one direction and with the other of said abutments to limit the angular movement in the opposite direction.

In a preferred arrangement, the control magnet is a horseshoe shape with its limbs extending at their ends parallel with the spindle of a moving assembly and each into the path of two abutments, respectively, on the moving assembly.

An example of this latter arrangement is illustrated by the accompanying diagrammatic drawings of which:

Figure 1 is a fragmentary plan view,

Figure 2 is a sectional elevation on the line 2-2 of Figure 1, and

Figure 3 is a side elevation from the right hand side of Figure 1 of part of a moving magnet type instrument movement incorporating this form of the invention.

The three figures are not drawn to scale and are greatly enlarged to show the construction more clearly.

All the parts are carried by a rigid frame ll of non-magnetic material. On the flat upper face of frame II a dial plate, indicated at I2, is secured by screws l3, I3. The upper part of the spindle of the moving assembly which is indicated at I5 has keyed thereto a non-magnetic gear wheel 20 Via which motion i transmitted to a pointer or o her indi a o n t s own). and supported by a vetype bear ng member 5. Bearing me ber I 6 is t e ded a d m y b adjusted by means of slo 16a The lower end o the m v n ssembly 5. omprises any wellknown type of moving magnet M.

he gear w eel 20 i f med with two diamet- ,rica ly oppos dar u te slots Z6, 26 (Figure 1) each ubtendms an angle s mewha greater than ninety degrees at he center and into and throush whichdepend the ends, respectively, of an inverted U-shaped magnet 21. The circumferential lengths of the slots 26 and the corresponding dimension, or with, of the ends of the magnet 21 are such as to limit the permitted angular movement to substantially 90 degrees by cooperation of the ends of the slots 26 as abutments with the ends of the magnet 21, the latter being the means which affords the control torque acting on the magnet M of the moving assembly. As is well understood, this control torque results from the flux of magnet 21 passing through the magnet I4.

The magnet 21 is formed with a dished annular central portion 21a (Figures 1 and 2) which, with the adjacent laterally extending parts thereof, is located between the underside of the dial plate I2 and a cut away part of the upper face of the upper transverse limb of the frame I I (Figure 2), the arrangement being such that when the screws l3, l3 which hold the dial plate 12 in position are tightened, the dished part 21a of the magnet is flattened (the dishing is exaggerated in Figure 2 for the sake of clearness) to such a degree that the magnet I I is firmly held frictionally, though not so tightly as to prevent deliberate shifting thereof for the purpose of adjustment. It is to be understood that in Figure 1 the plate [2 is omitted. It is to be noted that any zero adjustment of the movement will at the same time adjust correspondingly both limits of permitted movement of the moving magnet 14. If desired, although this is not shown in the drawings, provision may be made for shifting the magnet 21 at will to adjust "zero from the upper face of the dial plate [2 or from outside a. casing (not shown) in which the movement is enclosed.

We claim:

1. In an electrical instrument movement having a moving assembly comprising a spindle and a magnet fastened on said spindle, a control magnet arranged to exert a control torque on the a moving assembly, a mounting for the control magnet. the mounting means being arranged to allow for adjustment of the control magnet to set the zero position of the moving assembly, the control magnet and the moving assembly having parts which co-act with one another at difierent angular positions of said assembly and so limit the permitted movement of the latter, whereby adjustment of the control torque magnet to shift the zero position of the moving assembly at the same time shifts in the same direction both limits of the permitted movement of the moving assembly.

2. An electrical instrument movement as claimed in claim 1, wherein the moving assembly has two spaced abutments and wherein the control magnet extends at one end into the path of said abutments to co-act with the one abutment to limit the movement of the moving assembly in the one direction and to co-act with the other abutment to limit the movement 01 the moving assembly in the opposite direction.

3. An electrical instrument movement as claimed in claim 2, wherein the control magnet is substantially horse shoe shaped and is mounted with its limbs extending parallel with the spindle of the movin assembly each into the path of two spaced abutments, respectively, of the moving assembly.

4. In an electrical instrument movement, a fixed assembly comprising a rigid frame, a dial plate secured to the upper part of the frame, a moving assembly comprising a spindle supported '4 by bearing members on the frame, and an abutment member mounted on the spindle for rotation therewith, the latter being formed with two diametrically opposed arcuate slots centered at the spindle, and a substantially horse shoe shaped control magnet which straddles the upper part of the frame and is held frictionally between the latter and the dial plate with its ends depending into two arcuate slots, respectively, of the member fast on the spindle, whereby the control torque magnet serves, by cooperation with the ends of said slots or abutments to limit the permitted angular movement of the moving assembly as well as to determine the zero position of said assembly in accordance with the angular position of said control magnet about the spindle axis.

GEORGE N. HARDING. OTTO FRANZ WILHELM THAL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 440,291 Weston Nov. 11, 1890 570,454 Coleman Nov. 3, 1896 1,118,678 Patrick Nov. 24, 1914 2,326,252 Rich Aug. 10, 1943 2,380,609 Pearce July 31, 1945 2,478,329 Shaper Aug. 9, 1949 2,493,376 Zar Jan. 3, 1950 

